A gear machine comprises two gearwheels, which mesh with one another in external engagement, wherein they are surrounded by a housing. The housing is preferably provided with a high pressure port and a low pressure port. When the gear machine is operated as a pump, a rotary motion is imparted to the gearwheels, e.g. by means of an electric motor, and hydraulic fluid, in particular hydraulic oil, flows from the low pressure port to the high pressure port. When the gear machine is operated as a motor, hydraulic fluid flows from the high pressure port to the low pressure port, and a rotary motion is imparted to the gearwheels. One gearwheel is preferably provided with a drive journal, which projects from the housing.
A corresponding gear machine is known from DE 10 2012 206 699 A1. At least one gearwheel has a bearing journal, which is accommodated rotatably in an associated bearing bore. The bearing bore is arranged in a separate bearing body, which has a circular-cylindrical outer surface segment, which is associated with the gearwheel and by means of which it rests on an associated bearing surface on the inside of the housing. Opposite the tooth tips of the gearwheels there is furthermore a sealing surface, which is arranged on the inside of the housing.
Typically, the outer surface segment, the bearing surface and the sealing surface are of circular-cylindrical design, wherein the bearing surface and the sealing surface are arranged so as to be flush. During operation of the gear machine, the aim is that at least one tooth tip of each gearwheel should rest on the associated sealing surface in each rotational position of the gearwheels. This is typically achieved by means of a run-in operation, in which the gear machine is filled with pressurized fluid, in particular hydraulic oil, being operated with the maximum permissible operating pressure. During this process, material is removed by the tooth tips of the gearwheels from the associated sealing surface, giving rise to a clearly visible run-in trace. The run-in operation is complete when no more removal of material takes place.
The removal of material and hence the duration of the run-in process are dependent on the precise dimensions of the diameter of the bearing journal, the bearing bore, the outer surface segment, the bearing surface and the sealing surface. Said diameters can only be produced with a tolerance that differs from zero. The removal of material or run-in depth is furthermore dependent on the elastic deformation caused by the pressure forces of the pressurized fluid on the gear machine.